1. Field of the Invention
This invention pertains to a camera, and more particularly to a camera employing a film cartridge that can display the status of the film, including whether or not the film has been exposed.
2. Description of the Related Art
Among the types of film cartridges mounted in a camera is a cartridge having a bar code disk that displays film information, including film type (negative/positive, color/monochrome, etc.), film speed, number of exposure flames, etc. This bar code disk is affixed to one end of the spool used for winding the film, and is externally visible. The camera reads this film information and uses it as data on which to determine the conditions of photo-taking. In other words, when the film cartridge is mounted in a camera, the spool of the film cartridge is made to rotate, and the bar code formed on the bar code disk is read by a sensor contained in the camera.
On the other hand, a film status display plate that displays the status of the film, such as whether or not the film has been exposed, is affixed to the other end of the spool. The film status is displayed by means of the position (angle) at which the display plate stops so that the film status may be seen at a glance. Furthermore, because a bar code disk is also affixed to the spool, the film status may also be known from the position at which this bar code disk stops.
In a camera in which this type of film cartridge is used, it is preferable for the camera itself to automatically determine the film status to prevent double exposure, etc. This automatic determination can be made by reading the bar code disk. In other words, the film status may be determined by driving the spool so that the bar code disk rotates while the bar code is read using a sensor and by seeking the initial position (angle) based on the bar code read until a prescribed bar code display appears. This determination method is superior in that it allows determination of the film status by employing the sensor for the reading of the bar code.
However, in this method, if the power to the control circuit is cut off while the spool is rotating because the battery is removed from the camera, for example, the film status display becomes incomplete during said rotation. Moreover, the data read up to that point is lost. Consequently, even if a new battery is mounted, since only the bar code beginning from the position at which the rotation terminated is known, the camera cannot determine the film status.